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  • Physics  (23)
  • Wiley-Blackwell  (23)
  • Elsevier
  • 1980-1984  (23)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 9-25 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: PVC has been cyclopentadienylated by two conventional basic, LiCp and NaCp, and a new acidic, Me2CpAl, cyclopentadienylating agent. PVCs treated with basic cyclopentadienylating agents undergo severe random dehydrochlorination and exhibit a significant decrease in thermal and thermooxidative stability. In contrast, according to ozonization and degradation experiments, Me2CpAl does not cause dehydrochlorination during cyclopentadienylation. The thermal stability of PVC treated with relatively high concentrations of Me2CpAl and Me3Al at 25°C markedly increases due to substitution of labile chlorines in PVC with methyl groups. Initial thermal dehydrochlorination behavior of virgin PVC and samples treated with Me2CpAl at -30°C are similar. In contrast, thermooxidative stability decreases on Me2CpAl treatment at -30°C; this is attributed to ease of oxidation of pendant cyclopentadienyl groups; that is, the formation of peroxy radicals that may initiate dehydrochlorination by attacking unchanged repeat units in PVC. Acceleration of thermal dehydrochlorination disappears and the length of polyene sequences is reduced on Me2CpAl and Me3Al treatment. These observations are attributed to differences in rates of protonation-deprotonation; that is, rates of reinitation of zipping of treated and untreated PVCs during thermal degration. The effect of traces of aluminum residues on degradation of modified PVCs, however, cannot be neglected.
    Additional Material: 11 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 679-685 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Colorless poly(vinyl chloride)s (PVC) containing up to 1.6 allylic chlorines per molecule have been prepared by controlled random dehydrochlorination with a strong base. The effect of temperature in the -50 to +24°C range on the number of allylic chlorines and color of PVC has been investigated by ozonization experiments and UV-visible spectroscopy. A two-parameter kinetic model has been developed which quantitatively accounts for the observations and points the way for further research.
    Additional Material: 2 Ill.
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  • 3
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α,ω-Diphenylpolyisobutylenes produced by the Clt-R-Clt/ø3Al initiating system have been derivatized. Model chloromethylation of t-butylbenzene by CH3OCH2Cl in chloroform indicated that beyond ca. 35% yield significant alkylative side reactions occurred. Phenyl end groups (average 1.5 per chain) and unsaturated chain ends (from proton elimination) have been converted to carboxyl end groups by oxidation with RuO4 in chloroform. Subsequently the carboxyl end groups were converted to acyl chloride termini by reaction with SOCl2. The latter end groups were coupled with living polystyryl anions to form isobutylene-styrene blcok copolymers.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of isobutylene using ø3Al coinitiator and the tertiary chlorides tert.-butyl chloride (t-BuCl) and 2,6-dichloro-2,6-dimethylheptane (Clt-R-Clt) initiators has been studied. Polymerization rates with the t-BuCl/ø3Al and Clt-R-Clt/ø3Al initiating systems were high in the -20 to -70°C range. Yields and molecular weights increased with decreasing temperature. As predicted by model experiments the extent of phenylation increases with decreasing temperatures. According to spectroscopic evidence the polyisobutylenes carry phenyl end groups.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1523-1537 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Detailed understanding of the mechanism of initiation and chain transfer in BCl3-coinitiated isobutylene polymerization led to the efficient synthesis of symmetric telechelic polyisobutylenes carrying ∼CH2C(CH3)2Cl groups at either end of the molecule Cl-PIB-Cl. The synthesis is based on the use of inifers, i.e., bifunctional initiator-transfer agents that effect controlled initiation and propagation in the absence of chain transfer to a monomer. Specifically, the synthesis of Cl-PIB-Cl was achieved by the p-dicumyl chloride/BCl3/isobutylene/CH2Cl2 system. According to the inifer mechanism each Cl-PIB-Cl contains two terminal tertiary chlorines and one phenyl group at the interior of the chains. The structure of this new symmetric telechelic polymer has been established by detailed characterization studies including a sensitive new gel permeation chromatography (UV plus RI) analysis method, 1H-NMR, kinetic experiments, and chemical derivatization. The Cl-PIB-Cl molecule is a key intermediate for the synthesis of hosts of new materials, e.g., triblock copolymers, α,ω-diolefins, and α,ω-difunctional polymers.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a new glassy-rubbery-glassy triblock copolymer poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) has been demonstrated. The key to the synthesis was the preparation by inifer method of a perfectly bifunctional polyisobutylene which carries tert-chlorine end groups Cl-PIB-Cl. In conjunction with Et2AlCl coinitiator, the telechelic Cl-PIB-Cl molecule initiates the polymerization of α-methylstyrene at both ends of the prepolymer. Triblock composition can be controlled by the judicious selection of synthesis conditions; that is, Cl-PIB-Cl molecular weight, α-methylstyrene concentration, and solvent polarity. Theoretical triblock Mn calculated from Mn of Cl-PIB-Cl and triblock overall composition is in excellent agreement with experimental Mn which indicates negligible homopolymer contamination. Extraction with a series of hydrocarbon solvents reveals broad composition distribution. The stress-strain profile of a triblock is similar to that of a poly(styrene-b-butadiene-b-styrene) thermoplastic elastomer of similar composition.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1685-1692 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal dehydrochlorination of polychloroprenes and modified polychloroprenes was studied and was found to be rapid, readily reproducible, and reliable for the characterization of these rubbers. The rates of thermal dehydrochlorination of polychloroprenes and modified polychloroprenes are first order at 190°C under nitrogen. Significantly, the plot of dehydrochlorination rate (VHCl) versus dehydrochlorination extent (ζHCl) for polychloroprenes shows three regions. These data may be attributed to three dehydrochlorination regimes associated with four contributing repeat structures that have been identified by 13C-NMR spectroscopy: In contrast to polychloroprene, VHCl vs. ζHCl plots for modified (cyclopentadienylated and grafted) polychloroprenes, i.e., polychloroprenes that do not contain allylic chlorines, exhibit only one region suggesting only one dehydrochlorination mechanism in these materials. The slopes of the VHCl vs. ζHCl plots of the modified polychloroprenes are virtually identical. Moreover, the slopes of the VHCl vs. ζHCl plots for modified polychloroprenes and that of the latest of the three regions for unmodified polychloroprene are indistinguishable. This similarity in the VHCl vs. ζHCl curves suggests dehydrochlorination by a fundamentally similar mechanism in these materials, most likely one involving the —CH2—C(Cl)=CH—CH2— structure common to all of them. Concentration of labile chlorines in polychloroprene may be estimated by the differences in the dehydrochlorination kinetics of polychloroprene and modified polychloroprenes.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2721-2728 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparatory for the synthesis of terminally functional polyisobutylenes carrying one or two phenyl end groups, model experiments have been carried out using novel tert-butyl chloride/triphenylaluminum and 2,6-dichloro-2,6-dimethylheptane/triphenylaluminum initiating systems. As anticipated, t-BuCl was phenylated by ø3Al and the product is tert-butylbenzene. The reaction is extremely rapid and temperature has little effect on it in the 0 to -60°C range. The interaction between the 2,6-dichloro-2,6-dimethylheptane and ø3Al was found to be complicated by a proximity effect which leads to proton elimination in addition to phenylation. The formation of the desired diterminally phenylated product is not quanititative even at -60°C.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for the convenient synthesis of linear poly(β-pinenes) that carry one or two tert-chloro end groups (∼Clt) and three-arm star poly(β-pinenes) that carry three termini have been worked out. Specifically, the polymer with one ∼Clt end group was prepared by the H2O/BCl3 system, whereas those with two and three ∼Clt termini were prepared by the use of p-dicumyl chloride and sym-tricumyl chloride/BCl3 inifer combinations. The ∼Clt-terminated polymers were dehydro-chlorinated to yield the corresponding olefins. The molecular weights of the products were low enough to permit infrared (IR) and quantitative 1H-NMR investigations. Poly(β-pinene-b-tetrahydrofuran) diblock copolymers have been synthesized by inducing the polymerization of tetrahydrofuran (THF) by the Pβ—Clt/AgCF3SO3 initiating system.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 3573-3590 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel aromatic-telechelic polyisobutylenes were prepared and characterized: α,ω-diphenylpolyisobutylene, α-phenyl-ω-tolylpolyisobutylene, and α,ωditolylpolyisobutylene. The syntheses involved the preparation of asymmetric telechelic prepolymers (α-phenyl-ω-tert-chloropolyisobutylene and α-tolyl-ω-tert-chloropolyisobutylene) by the minifer method and quantitative alkylation of benzene and toluene by the prepolymer. The terminal aromatic rings of these telechelic polyisobutylenes were quantitatively nitrated, acetylated, and chlorosulfonated and a series of further novel telechelic products was obtained. Characterization of these derivatives provided additional proof for the telechelic structure of the starting prepolymers. The quantitative reduction of nitroaryl-telechelic polyisobutylene by SnCl2/HCl led to aminoaryl-telechelic polyisobutylene which was used to cure bisphenol-A diglycidyl ether. These new flexible epoxy networks exhibited outstanding heat and hydrolytic stability combined with satisfactory mechanical properties.
    Additional Material: 13 Ill.
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